On 08.07.20 11:45, Mike Rapoport wrote: > On Wed, Jul 08, 2020 at 11:25:36AM +0200, David Hildenbrand wrote: >> On 08.07.20 11:15, Mike Rapoport wrote: >>>>>>>> >>>>> But on more theoretical/fundmanetal level, I think we lack a generic >>>>> abstraction similar to e.g. x86 'struct numa_meminfo' that serves as >>>>> translaton of firmware supplied information into data that can be used >>>>> by the generic mm without need to reimplement it for each and every >>>>> arch. >>>> >>>> Right. As I expressed, I am not a friend of using memblock for that, and >>>> the pgdat node span is tricky. >>>> >>>> Maybe abstracting that x86 concept is possible in some way (and we could >>>> restrict the information to boot-time properties, so we don't have to >>>> mess with memory hot(un)plug - just as done for numa_meminfo AFAIKS). >>> >>> I agree with pgdat part and disagree about memblock. It already has >>> non-init physmap, why won't we add memblock.memory to the mix? ;-) >> >> Can we generalize and tweak physmap to contain node info? That's all we >> need, no? (the special mem= parameter handling should not matter for our >> use case, where "physmap" and "memory" would differ) > > TBH, I have only random vague thoughts at the moment. This might be an > option. But then we need to enable physmap on !s390, right?
Yes, looks like it. > >>> Now, seriously, memblock already has all the necessary information about >>> the coldplug memory for several architectures. x86 being an exception >>> because for some reason the reserved memory is not considered memory >>> there. The infrastructure for quiering and iterating memory regions is >>> already there. We just need to leave out the irrelevant parts, like >>> memblock.reserved and allocation funcions. >> >> I *really* don't want to mess with memblocks on memory hot(un)plug on >> x86 and s390x (+other architectures in the future). I also thought about >> stopping to create memblocks for hotplugged memory on arm64, by tweaking >> pfn_valid() to query memblocks only for early sections. >> >> If "physmem" is not an option, can we at least introduce something like >> ARCH_UPDTAE_MEMBLOCK_ON_HOTPLUG to avoid doing that on x86 and s390x for >> now (and later maybe for others)? > > I have to do more memory hotplug howework to answer that ;-) > > My general point is that we don't have to reinvent the wheel to have > coldplug memory representation, it's already there. We just need a way > to use it properly. Yes, I tend to agree. Details to be clarified :) -- Thanks, David / dhildenb
